The invention relates to a cage-type intervertebral implant, and also to a method for its production.
It relates to a vertebral column implant and its method of production, the implant being used for insertion between two vertebrae of the vertebral column. It serves as a means of fusion (arthrodesis) of the two vertebral bodies through which the original intervertebral disk height is restored and also the neural foreamen return to their original size.
The individual vertebrae of the vertebral column have a vertebral body, a vertebral arch, a spinous process, two transverse processes, and two upper and two lower articular processes. The vertebrae are connected to the abutting intervertebral disks (disci intervertebralis) and give rise to the vertebral body (corpus vertebrae). The intervertebral disk consists of liquid-rich fibrous cartilage and connects the individual vertebral bodies with each other. The size of the intervertebral disks increases from top to bottom, corresponding to the loads arising in the human body. The intervertebral disks serve as elastic buffers and reislently damp impacts.
It is known that the intervertebral disks can become displaced, or that the inner gelatinous core (nucleus pulposus) can emerge through cracks in the cartilaginous outer ring (annulus fibrosus), which is similar to connective tissue. The intervertebral disk can then partially enter the inververtebral foramina (foramina intervertebralia) or into the spinal canal. Furthermore, this prolapse can be dorsal, medial, or lateral. Such prolapses most frequently occur at the L4-L5-S1 and C6-C7 vertebrae. If such prolapses are not treated, irreversible pressure damage of nerve roots, foramina or transverse lesions, result. If physiotherapy according to the symptoms, e.g., remedial exercises or massage, show no promise of success, the intervertebral disk (discuss intervertebralis) has to be surgically removed. There now exist the possibility of implantation of such an implant (cage), by means of which an arthrodesis between the two vertebral bodies can take place.
An intervertebral implant is known from EP 0916323-A1 which has a bean-shaped structure and can be inserted between two vertebrae. The implant has a wedge shape, conferred by a different height of the two longitudinal sidewalls. The walls surrounding the implant are provided with rows of holes in order to promote the ingrowth of bone tissue.
It is disadvantageous that the implant has a wedge shape in only one direction, and is expensive to manufacture because of the many laterally formed holes.
Furthermore, cage structures are known under the designation xe2x80x9cBrantigan cagexe2x80x9d structures are known which have many teeth on their cage surfaces in order to prevent an undesired displacement of the cage. Made of polyether ether ketone (PEEK), as so-called PEEK moldings, they have inadequate strength, which can lead to breakage of the cage structure under load. A single thread is provided to receive instruments, resulting in unsatisfactory instrument manipulation.
A relatively small moment of tilt is conferred by the cuboidal geometry, with disadvantageous effects.
The invention has as its object to provide a cage-type intervertebral implant which is characterized by a double wedge geometry defined by two lordosis angles which ensures an improved instrument manipulation.
A further object of the invention consists of the production of such an implant.
According to the invention, this object is attained with an implant according to the wording of patent claim 1 and by a method of production of the same according to the wording of patent claim 23.